5.2 Cable stayed deck erection
The main cable stayed bridge was constructed by the balanced cantilever technique , working on the two fronts away from each of the three towers .
Installation started with temporary falsework legs and platforms that were installed at each tower and four permanent segments were installed . The deck starter segments were erected at each of the towers once the towers had reached the 18 th of the 54 lifts in total ( 210m ). After their installation they received temporary attachments to allow for the Erection Traveller ( ET ) to be installed .
The main deck segments are lifted up from the river into position by the ET . Each lift is typically a 16.2m long deck segment complete with the reinforced posttensioned concrete deck . The transverse in-situ welded joints , cable stay installation , and a short insitu concrete deck stitch are carried out and the ET is moved along the cantilever for the next lift . The composite decks were adequately cured and the lateral post tensioning applied . Finally , closure segments are installed between the cantilevers .
The first of the cable stays , at Lift 38 , was installed once the towers reached Lift 40 . The temporary tower leg trestles were installed to provide support to the temporary works platforms and deck works prior to the installation of the stay cables .
In deck erection six erection travellers ( ET ) were utilised simultaneously , one each positioned at the cantilever ends . With the exception of the starter segments , all cable supported deck segments were erected from a delivery barge .
Deck deflection increased significantly as the deck cantilever lengthens . At its maximum extent , cantilever deflection were 2m requiring four strokes of the 500mm strand jack to overcome this deflection alone .
Figure 20 : Taklift 6 lifting the Erection Traveller onto Central Tower starter segments
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